The intelligence of fraternal twins raised in the same home is more similar than the intelligence of nontwin siblings raised in the same home. This finding provides evidence for the effects of environment on intelligence because fraternal twins and other siblings have the same degree of genetic relatedness.

Question

Quizplus · Accepted Answer

Fraternal twins share the same environment but only about 50% of their genes, while nontwin siblings share about 50% of their genes but may have different environments due to birth order, age spacing, and other factors. Therefore, the fact that fraternal twins have more similar intelligence than nontwin siblings suggests that shared environment plays a role in intelligence, beyond genetic factors.

The Intelligence of Fraternal Twins Raised in the Same Home